Method for analyzing refrigerant properties

ABSTRACT

One or more properties of a refrigerant sample, such as composition, purity or both composition and purity, are analyzed for purposes of refrigerant recovery and reuse by providing a refrigerant cell having a chamber for containing a refrigerant sample and a passage for connecting the chamber to a source of refrigerant in vapor phase. The sample chamber and passage are evacuated, and the chamber and at least a portion of the passage contiguous with the chamber are cooled until the temperature thereof reaches a predetermined temperature at or below ambient temperature. After the chamber and passage have been evacuated and cooled, the passage is connected to a source of refrigerant in vapor phase such that a refrigerant vapor sample is drawn into the chamber and condensed to liquid phase. After the cell chamber has been filled with a liquid refrigerant sample, one or more desired properties of the liquid refrigerant sample are measured or detected.

The present invention is directed to refrigerant handling systems, andmore particularly to a method and apparatus for analyzing properties ofrefrigerants such as refrigerant make-up or composition.

BACKGROUND AND OBJECTS OF THE INVENTION

It is now widely recognized and accepted that release into theatmosphere of chlorofluorocarbon(CFC)-based andhydrochlorofluorocarbon(HCFC)-based refrigerants has a deleteriouseffect on the ozone layer that surrounds the earth. Production ofCFC-based and HCFC-based refrigerants is to be severely curtailed in thefuture, and the cost of refrigerant for service purposes is alreadyincreasing. It has therefore become standard practice in therefrigeration system service industry to recover, recycle and reuse therefrigerant in the refrigeration system under service, or to recover,store and reclaim the refrigerant for later reuse, rather than merely tovent such refrigerant into the atmosphere and replace with newrefrigerant as had been common practice in the past. U.S. Pat. Nos.4,768,347, 4,805,416 and 4,878,356, all assigned to the assignee hereof,disclose equipment for recovering, recycling and/or rechargingrefrigerant in a refrigeration system service environment.

As currently envisioned R-12 refrigerant is being replaced by differenttypes of refrigerants in production of new refrigeration systems. Forexample, R-12 refrigerant is being replaced by R-134a refrigerant in theautomotive industry--i.e., in automotive air conditioning systems.However, because these refrigerants and their associated lubricants arechemically incompatible with each other, inadvertent mixture of evensmall amounts of the different refrigerants can cause severe damage andearly failure of the refrigeration system. It has been proposed toprovide different service fittings on refrigeration equipment usingdifferent types of refrigerants, but the use of adapters and the like inthe service industry may still result in inadvertent mixing ofrefrigerant/lubricant types, with consequent damage to the system underservice and to the service equipment itself. A further complicationarises with the use of intermediate refrigerants as substitutes for R-12refrigerant, such as ternary blends made by DuPont. With severecurtailment of R-12 production in the future, it is anticipated that asignificant number of refrigeration systems currently employing R-12refrigerant may eventually be retrofitted with an intermediatesubstitute refrigerant. Inadvertent mixing of refrigerants is consideredto be an irreversible process, leading to disposal of the mixedrefrigerant as hazardous waste.

The various types of refrigerants therefore need to be kept separate toprotect the integrity of the service equipment, and to ensure properintegrity and performance of the refrigeration equipment under service.Use of an incorrect refrigerant or an undesired mixture of refrigerantscan occur due to charging the incorrect refrigerant into therefrigeration equipment during installation or service, selectiveleakage or purging of one refrigerant component in a non-azeotropicrefrigerant mixture, incomplete removal of the previous refrigerant inretrofitting equipment or clearing of the recovery/recycling servicesystem, chemical reaction within the refrigerant such as during a hightemperature mechanical failure or hermetic compressor burnout generatingundesirable refrigerant by-products, or inadvertent mixing by recoveryof refrigerant into an incorrect container or incorrect consolidation ofrecovered refrigerants into a larger container for shipment to a reclaimprocessing center.

In the past, refrigerant analysis has been accomplished by drawing aliquid refrigerant sample and sending the sample to a fully equippedrefrigerant chemistry laboratory. An experienced chemist can remove somecontaminants, such as oil, water and metallic particles, and thenanalyze the refrigerant using gas chromatography, mass spectroscopy orinfrared spectroscopy. Air-Conditioning and Refrigeration InstituteStandard 700-88 Specifications for Fluorocarbon Refrigerants specifiesanalysis of a liquid refrigerant sample. However, such laboratoryanalysis requires several hours or days to obtain, and is thus notsuitable for use in the field. There is therefore a need in therefrigeration system service industry for a device that can be employedto test refrigerant in a storage container, or in a refrigeration systembefore performing service on the system, that is not restricted to anyparticular type of refrigerant or to automotive service applications,that is particularly well adapted to identify and distinguish betweenrefrigerants of different types, that is inexpensive to manufacture andmarket, that is readily portable, that is rapid and efficient inoperation, and/or that can be employed by relatively untrained servicepersonnel.

U.S. Pat. No. 5,158,747, assigned to the assignee hereof, discloses adevice for identifying and distinguishing between and among refrigerantsof different types. The device includes a fixed volume for containing asample of refrigerant. The refrigerant to be tested is selectivelyadmitted into the volume in vapor phase, vapor pressure of refrigerantwithin the fixed volume is measured, and admission of refrigerant isterminated when the vapor pressure of refrigerant contained in thevolume reaches a preselected level. A sensor and associated electronicsare coupled to the sample-containing volume for determining type ofrefrigerant vapor as a function of one or more selected properties ofthe refrigerant, and indicating such refrigerant type to an operator.U.S. Pat. No. 5,295,360, also assigned to the assignee hereof, disclosesan improved apparatus in which a thermistor provides a first electricalsignal as a function of the combined effect of thermal conductivity andtemperature of a refrigerant vapor sample in the sample-containingvolume, and a temperature sensor provides a second electrical signal asa function of temperature of the refrigerant vapor sample essentiallyindependent of thermal conductivity. Associated electronics determinetype of refrigerant in the sample-containing volume as a function of thefirst and second electrical signals, and thus as a function of thermalconductivity of the refrigerant sample independent of sampletemperature.

It has heretofore been proposed to employ near infraredspectrophotometric analysis techniques for determining refrigerantmake-up or composition. A liquid phase refrigerant sample is fed to aboiler, where the refrigerant sample is vaporized to separaterefrigerant from oil and water. The refrigerant vapor is fed to a samplecell, where the vapor is condensed and subjected to near-infraredspectrophotometric analysis. Refrigerant make-up (i.e., refrigerant typeor mixture of types) is determined by comparison of the near-infraredabsorption spectra of the sample with prestored spectral datarepresentative of known refrigerant types. Although the technique soproposed can provide an accurate indication of refrigerant type ortypes, improvements remain desirable. In particular, simplification isdesirable to adapt the technique for use in the field. For example, theliquid phase refrigerant sample can contain up to twenty percentlubricant as well as dirt and metal particles, which can affectprecision of the measurement process. The possible introduction oflubricant and particulates also necessitates cleaning of the testchamber or cell between uses.

U.S. application Ser. No. 08/160,224, now U.S. Pat. No. 5,371,019, alsoassigned to the assignee hereof, discloses a method and apparatus foranalyzing one or more refrigerant properties by evacuating a refrigerantsample vessel or cell, drawing a sample of refrigerant vapor into thevessel, and condensing the refrigerant sample within the vessel formeasuring and indicating one or more desired properties of therefrigerant sample in liquid phase. By drawing the sample refrigerant invapor phase rather than liquid phase as theretofore proposed, the samplewill be relatively free of lubricant, particulate and watercontamination. The sample cell can be readily cleaned by simpleevacuation in preparation for the next measurement cycle. The disclosedtechnique is also greatly simplified as compared with previousapproaches by eliminating the necessity for boiling a liquid refrigerantsample. Although the technique so disclosed in the copending applicationadvances the state of the art for the reasons indicated, furtherimprovements remain desirable. In particular, difficulties areencountered, for differing refrigerants and differing levels ofnon-condensible contamination, in completely filling the chamber of thetest vessel or cell with a liquid phase refrigerant sample. It is ageneral object of the present invention to provide a method andapparatus for analyzing refrigerant properties, in which theefficiency--i.e., the time duration and completeness--of thecell-filling operation is greatly enhanced as compared with the priorart.

SUMMARY OF THE INVENTION

One or more properties of a refrigerant sample, such as composition,purity or both composition and purity, are analyzed for purposes ofrefrigerant recovery and reuse in accordance with the present inventionby providing a refrigerant sample vessel or cell having a chamber forcontaining a refrigerant sample and a passage for connecting the chamberto a source of refrigerant in vapor phase. The sample chamber andpassage are evacuated, and the chamber and at least a portion of thepassage contiguous with the chamber are cooled until the temperaturethereof reaches a predetermined temperature at or below ambienttemperature. After the chamber and passage have been evacuated andcooled, the passage is connected to a source of refrigerant in vaporphase, such that a refrigerant vapor sample is drawn into the chamberand condensed to liquid phase. After the cell chamber has been filledwith a liquid refrigerant sample, one or more desired properties of theliquid refrigerant sample are measured or detected.

In the preferred embodiment of the invention, the refrigerant passagethat is cooled with the sample chamber is provided with the samplechamber in a cell block. The passage is separate from and tangential tothe sample chamber within the cell block, and has a length at leastequal to diameter of the sample chamber. The cell block passage opens tothe sample chamber at the lower portion of the chamber. Thus, therefrigerant is pre-cooled as it passes through the cell block passage tothe sample chamber. A purge port is connected to the upper portion ofthe sample chamber for purging non-condensibles, which assists thefilling process in situations of high concentration of air in therefrigerant sample, for example. The non-condensibles are purged throughan orifice for controlling rate of purging. Light absorption in themid-and far-infrared ranges may be employed to determine when the testchamber is full of liquid refrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objects, features and advantagesthereof, will be best understood from the following description, theappended claims and the accompanying drawings in which:

FIG. 1 is a schematic diagram of a refrigerant analysis apparatus inaccordance with a presently preferred embodiment of the invention; and

FIG. 2 is a graphic illustration of test results that demonstrateimproved filling of the sample test chamber in accordance with theembodiment of the invention illustrated in FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 illustrates an apparatus 10 for analyzing refrigerant inaccordance with a presently preferred embodiment of the invention ascomprising a vessel or cell block 12 for receiving and holding arefrigerant sample. Cell block 12 has an inlet port 14 connected by aconduit 16 to a coupling 18 for connection to a source of refrigerantvapor. Coupling 18 preferably comprises a self-sealing quick-disconnectcoupling such as illustrated, for example, in U.S. Pat. Nos. 5,080,132and 5,248,125. A thermoelectric heater/cooler 20 couples cell block 12to a block of cooling fins 22. A sensor 24 is also coupled to cell block12 for measuring one or more properties of refrigerant containedtherewithin. Sensor 24 in the preferred embodiment of the inventioncomprises a source of near-infrared light and suitable filter/sensorunits for illuminating refrigerant within cell block 12 and obtainingspectral photometric absorption data as a function of wavelength.

Within cell block 12 there is formed a central chamber or cavity 26 forholding a refrigerant test sample. A passage section 28 extends fromcell block inlet port 14 along one side of the cell block tangential tochamber 26 to a second passage portion 30 that extends along a secondside of cell block 12 again tangential to chamber 26 and at right angleto passage portion 28. Passage portion 30 connects with a chamber inlet32 at the lower end of the chamber. A purge port 34 opens through cellblock 12 from the upper end of chamber 26, and is connected through asolenoid valve 36 and an orifice 38 for purging chamber 12 toatmosphere. A temperature sensor 40 is operatively coupled to cell block12 for providing an electrical signal as a function of temperature ofchamber 26 and passage sections 28, 30 within the cell block. Solenoidvalve 36, temperature sensor 40 and thermoelectric heater/cooler 20 areall connected to an electronic control unit 42. Control 42 receives atemperature threshold input 44, and drives a display 46 for indicatingone or more properties or parameters of the refrigerant under test,including temperature of cell block 12 from which refrigeranttemperature is inferred, and one or more properties related tocomposition, purity or both composition and purity of the refrigerantwithin cell chamber 26.

In operation, sample cell 12 is first evacuated. This may beaccomplished by connecting the vessel through coupling 18 to a vacuumpump 48, and then operating the vacuum pump to draw a vacuum (i.e.,sub-atmospheric pressure) within the sample cell and conduit 16.Pressure within the sample cell preferably is reduced below at least5,000 micrometers, and most preferably below 500 micrometers of mercuryabsolute, in order to ensure that the prior refrigerant sample and allcontaminants are removed from within the sample cell. Vaporization andevacuation of the prior refrigerant sample may be assisted by energizingthermoelectric heater/cooler 22, using control 26, to vaporize the priorrefrigerant sample.

Sample cell 12, including sample chamber 26 and refrigerant passagesections 28, 30, are then pre-cooled by operation of thermoelectricheater/cooler 20, again using control 42, until temperature of thesample cell decreases to a preselected temperature at or below ambienttemperature. This preselected temperature threshold is set at 44, andtemperature of cell block 12 is monitored through sensor 40 anddisplayed at 46. For example, when inlet refrigerant vapor temperatureis expected to be in the range of 55° to 120° F., the temperaturethreshold may be set at about 45° to 47° F.

After the temperature of cell block 12 has decreased to or below thetemperature threshold set at 44, coupling 18 is connected to a source oftest refrigerant in vapor phase. In FIG. 1, this source is illustratedas a refrigerant storage container 50 having a vapor port 52 connectedthrough a manual valve 54 to a fitting 56 that mates with coupling 18.Coupling 18 may be preconnected to fitting 56, and valve 54 opened whenthe sample cell is precooled. In this configuration, apparatus 10 isused to analyze refrigerant within storage container 50. The apparatusmay also be employed to analyze refrigerant within a refrigerationsystem under service, for example, by connecting coupling 18 to thesystem vapor port and opening the associated valve, if any.

Refrigerant vapor is drawn from within storage container 50 into testchamber 26 through conduit 16 and passage sections 28, 30 by the reducedpressure within the cell chamber, passage and conduit resulting from theprior evacuation process and reduced temperature of the cell block. Asthe refrigerant vapor flows through passage sections 26, 30 to chamber26, the refrigerant vapor is pre-cooled in the cell block passagesections. As will be shown in connection with FIG. 2, this pre-coolingof the inlet refrigerant vapor greatly enhances the efficiency of thefilling process. In situations where the filling process is slowed by alarge quantity of non-condensibles such as air in the incomingrefrigerant vapor, the filling process may be enhanced by opening valve36 so as to purge the non-condensibles from sample chamber 26. Purgingthrough orifice 38 helps control the rate of purging. An orifice size of0.004 to 0.005 inches has been found suitable. Refrigerant flows throughpassage sections 28, 30 into chamber 26 and is precooled by cell block12.

Any suitable technique may be employed to determine when chamber 26 isfull. For example, sensor 24 may be operated and monitored to indicatethat chamber 26 is full when light is absorbed by the liquid refrigerantto a predetermined level at a specified wavelength. When near-infraredwavelengths are employed for refrigerant analysis, one or morewavelengths in the mid- or far-infrared regions may be employed forindicating a full chamber. The light will, of course, be absorbed morestrongly by liquid phase refrigerant than by refrigerant vapor becauseof the increased number of light-absorbing refrigerant molecules.

With a liquid refrigerant sample now contained within cell chamber 26,infrared sensor 24 is operated by control 42 or measuring one or moreproperties of the refrigerant. Sensor 24 may be of any suitableconventional type for obtaining absorption data from the refrigerantsample, which data is then compared in control electronics 42 toprestored absorption data from known refrigerant types. Such absorptiondata comparisons shows not only the type of refrigerant within thevessel, but also whether the refrigerant sample is a mix of refrigeranttypes and whether the sample contains impurities (e.g., otherrefrigerants) that call for recycling or reclamation. Refrigerant typeand purity so determined are indicated at display 46. Heater/cooler 20preferably is operated by control 42 to maintain temperature withinchamber 26 substantially constant during operation of sensor 24. Host orall of the refrigerant sample may then be removed from cell block 12 byoperating heater/cooler 20 in a heating mode, which transfers a majorportion of the refrigerant back to vessel 50. Any refrigerant orcontaminates remaining in cell block 12 will be removed by subsequentconnection to vacuum pump 48 during the next sample/measurement cycle.Sensors 24 other than infrared sensors may also be employed, such as anx-ray defraction sensor, a thermal conductivity sensor, a sensor formeasuring dielectric properties of the refrigerant, a sensor formeasuring molecular weight by ultrasonic techniques.

FIG. 2 illustrates test results comparing operation of cell block 12employing passage sections 28, 30 as pre-cooling inlet passage sectionsas described in connection with FIG. 1 (configuration 2 in FIG. 2) withthe same cell 12a (configuration 1) in which passage sections 28, 30 areconnected as part of the purge path and incoming refrigerant is supplieddirectly to chamber 26 without pre-cooling. The remainder of FIG. 2consists of bar charts that illustrate filling efficiency (time andcompleteness) for various refrigerants, with or without entrained air.Both cell block 12 of configuration 2 and cell block 12a ofconfiguration 1 were pre-cooled in identical test set-ups, and inletrefrigerant temperatures and pressures were otherwise identical in bothcases. The only difference between the two test arrangements wasdisposition of cell block passage sections 28, 30 as pre-cooling inletpassages in configuration 2, and not in configuration 1. Sample cellfill time was determined by visually observing the cell chamber andterminating the test when no air bubble remained in the chamber.

For R-11 refrigerant heated to a pressure of 8 psig, the configuration 1cell arrangement had an air bubble 60 at the top of the cell chamberafter sixty seconds. When it was them attempted to purge the cellthrough a 0.005 inch orifice, the cell could still not be filled becausethe refrigerant was purging as fast as it was flowing into the cell.However, using the configuration 2 cell arrangement under the same testconditions, the cell filled without purging in thirty-one seconds andthirty-four seconds in two test runs.

For R-134a with no entrained air, the fill time for configuration 1 ofaround forty-nine seconds was improved to around nineteen seconds inconfiguration 2 without purging. For R-134a with five percent air, theconfiguration 1 cell arrangement required one hundred fifteen to onehundred forty seconds to fill with continuous purging after the initialsixty seconds, whereas the configuration 2 cell arrangement was filledin twenty-seven to twenty-eight seconds without purging.

For R-12 refrigerant with ten percent entrained air, the configuration 1cell arrangement would not fill even after purging. After one minute,the cell cross section 62 was still almost entirely filled with air, anda bubble 64 remained even after purging from three and one-half minutesto six minutes. The test was terminated after six minutes with thechamber still unfilled. With the configuration 2 cell arrangement, thecell chamber filled in one hundred three to one hundred five secondswith purging after sixty seconds. With purging for the firstthirty-eight seconds, the cell fill time was reduced to fifty-eightseconds, and purging for the first thirty seconds produced a cell filltime of forty-six seconds.

For R-22 refrigerant with no entrained air, the fill time for theconfiguration 2 cell arrangement was twenty-one seconds, as comparedwith thirty-eight seconds for cell configuration 1 without purging. Withpurging during the initial thirty seconds, the configuration 2 to cellarrangement required thirty seconds to fill. R-502 refrigerant was alsotested without entrained air, with results substantially the same as forthe R-22 refrigerant as illustrated in FIG. 2.

Thus, pre-cooling the incoming refrigerant by routing through pre-cooledcell passage sections 28, 30 in the temperature controlled test cellreduced the fill time by about fifty percent in situations where bothcell configurations would fill--i.e., the R-134a with and withoutentrained air, and the R-22 and R-502 tests. In the R-11 and R-12 tests,the pre-cooling passages of the present invention allowed filling of thetest cell, which would not otherwise fill.

We claim:
 1. A method of analyzing refrigerant that comprises the stepsof:(a) providing a refrigerant cell block having a chamber forcontaining a refrigerant sample, (b) providing refrigerant passage meansfor connecting said chamber to a source of refrigerant in vapor phase,at least a portion of said passage means contiguous with said chamberbeing disposed within said cell block separate from and adjacent to saidchamber, (c) drawing a vacuum in said chamber and said passage means,(d) cooling said cell block and said portion of said passage meanswithin said cell block simultaneously until temperature of said cellblock, and said portion within said cell block, reaches a predeterminedtemperature, (e) after said steps (c) and (d), connecting said passagemeans to a source of refrigerant in vapor phase, such that a refrigerantvapor sample is drawn into said chamber and condensed to liquid phase,(f) terminating said step (e) when said cell chamber is full ofrefrigerant in liquid phase, and (g) detecting one or more properties ofthe refrigerant in said chamber while the refrigerant is in liquidphase.
 2. The method set forth in claim 1 wherein said step (g) isaccomplished by subjecting the refrigerant sample in said chamber tonear-infrared spectrophotometric analysis.
 3. The method set forth inclaim 1 wherein said step (g) is accomplished by subjecting therefrigerant sample in said chamber to mid-infrared or far-infraredspectrophotometric analysis.
 4. The method set forth in claim 1 whereinsaid portion of said passage means provided in said step (b) is disposedin said cell block adjacent to and tangential to said chamber.
 5. Themethod set forth in claim 4 wherein length of said portion of saidpassage means disposed within said cell block is at least as great asdiameter of said chamber.
 6. The method set forth in claim 1 comprisingthe additional step, prior to said step (g), of: (h) purgingnon-condensibles from within said chamber and said passage portion. 7.The method set forth in claim 6 wherein said step (h) comprises the stepof purging non-condensibles from said chamber and said passage portionthrough an orifice to control rate of purging.